Make sure GLIDEIN_MaxMemMBs and GLIDEIN_CPUS are treated as float

[mambelli]

Is your feature request related to a problem? Please describe.
In PR #374 GLIDEIN_MaxMemMBs and GLIDEIN_CPUS become float after the overload adjustment
All variables in shell are strings so copying them around is not a problem
But there is some math involving these 2 that may still use let or (( )), both working only with integer values.
This should be checked and corrected to use bc or something else working also w/ floats.

NOTE that GLIDEIN_MaxMemMBs, GLIDEIN_CPUS_EXPECTED, and GLIDEIN_CPUS should remain integer values in the configuration so as not to complicate Glidein provisioning in the Frontend and monitoring

Describe the solution you'd like
To treat correctly GLIDEIN_MaxMemMBs and GLIDEIN_CPUS as float, using bc or something else working also w/ floats.

Describe alternatives you've considered
NA

Info (please complete the following information):

• Priority: high
• Stakeholders: CMS, FactoryOps
• Components: glidein, documentation

Additional context
NA